Re: bin/53285: Build times tripled with make/job.c 1.193

["Simon J. Gerraty" <sjg%juniper.net@localhost>]

The following reply was made to PR bin/53285; it has been noted by GNATS.

From: "Simon J. Gerraty" <sjg%juniper.net@localhost>
To: <gnats-bugs%NetBSD.org@localhost>
Cc: <gnats-admin%NetBSD.org@localhost>, <netbsd-bugs%NetBSD.org@localhost>,
        Andreas Gustafsson
	<gson%gson.org@localhost>, <sjg%juniper.net@localhost>
Subject: Re: bin/53285: Build times tripled with make/job.c 1.193
Date: Sun, 13 May 2018 10:59:30 -0700

 The patch below, is probably a better 1st step.
 It fixes the busy wait with no delay.
 
 It does still poll the job token pipe, but only when we would
 otherwise be busy waiting, rather when we have no need to.
 
 Index: job.c
 ===================================================================
 RCS file: /cvsroot/src/usr.bin/make/job.c,v
 retrieving revision 1.194
 diff -u -p -r1.194 job.c
 --- job.c	13 May 2018 12:10:36 -0000	1.194
 +++ job.c	13 May 2018 17:49:16 -0000
 @@ -2944,14 +2944,15 @@ Job_TokenWithdraw(void)
      count = read(tokenWaitJob.inPipe, &tok, 1);
      if (count == 0)
  	Fatal("eof on job pipe!");
 -    if (count < 0 && jobTokensRunning != 0) {
 +    if (count < 0) {
  	if (errno != EAGAIN) {
  	    Fatal("job pipe read: %s", strerror(errno));
  	}
  	if (DEBUG(JOB))
  	    fprintf(debug_file, "(%d) blocked for token\n", getpid());
 +	if (jobTokensRunning)
 +	    return FALSE;
  	wantToken = 1;
 -	return FALSE;
      }
  
      if (count == 1 && tok != '+') {